This invention relates generally to techniques for cleaning a magnetic tape reproducing device, and specifically to methods and apparatus for cleaning a rotary magneto-resistive head used in such reproducing devices.
The use of magneto-resistive (MR) head technology in conventional hard disk drive (HDD) units has resulted in increased recording densities. The MR head is beginning to appear in linear tape systems, as well. Application of MR head technology in helical scan tape systems has been suggested. However, in order to achieve sufficient reliability, better techniques for cleaning rotary MR heads can be developed.
As is well known, when foreign matter or dirt adheres to the surface of a rotary magneto-resistive head of a magnetic tape reproducing device, proper reproduction from the magnetic tape becomes difficult to carry out. Particularly, in a linear tape storage unit for a computer, foreign matter present on the surface of a magnetic head can result in system failure or data loss, for example. In helical scan systems, xe2x80x9chead clogxe2x80x9d can occur during read and write operations because of rubbing condition between head and tape. This phenomenon is attributable to the helical heads protruding from the upper drum in the wrapped tape on file drum. Head clog can cause an unreadable data situation during write-read mode, for example. This can result in failure to achieve normal reproduction of the stored information.
What is needed are improved techniques for cleaning rotary magneto-resistive heads.
According to the invention, techniques for cleaning a rotary magneto-resistive head are provided. Specific embodiments according to the invention can be especially useful in tape drive systems, and the like. Embodiments can provide methods and apparatus for cleaning contaminant from rotary magneto-resistive heads while guarding against damage to the head from excess cleaning, and the like. Specific embodiments can control the rotational speed of a rotary magneto-resistive head in order to facilitate cleaning operations. Embodiments can control a position as well as a force of contact between a cleaning mechanism and a rotary magneto-resistive head. Embodiments include a cleaning device and a control method, and are suited for use in a magneto-resistive head mounted on a rotary cylinder of a computer tape storage unit, for example, although application of the present invention is not limited to such embodiments.
It is an object of specific embodiments according to the present invention to provide relatively improved approaches to cleaning a rotary magneto-resistive head.
In a representative embodiment according to the present invention, an apparatus for cleaning a rotary magneto-resistive head is provided. The apparatus can include a cleaning roller supported by an actuator arm, in order to position the cleaning roller in and out of contact with at least the rotary magneto-resistive head. In some configurations, the cleaning roller can also contact a stationary portion of a rotating cylinder holding the rotary magneto-resistive head, for example. The apparatus can also comprise a cam coupled to the actuator arm in order to provide a linear motion for the cleaning roller. A mode motor can be coupled to the cam in order to provide motion. An error detector can be electrically coupled with the rotary magneto-resistive head to sense an error rate, for example. A read amplifier, electrically coupled with the rotary magneto-resistive head, can sense a presence of thermal noise in an output of the head. A control device can be coupled to the error detector, the read amplifier and the mode motor. The control device positions the cleaning roller in contact with the rotary magneto-resistive head by action of the actuator arm, the cam and under power of the mode motor, for example. The cleaning roller is positioned responsive to the error detector determining an error rate in excess of a threshold, and the like. The cleaning roller is positioned out of contact with the rotary magneto-resistive head responsive to the read amplifier determining a presence of thermal noise in excess of a threshold.
In another representative embodiment according to the present invention, an apparatus can comprise a motor driver speed control that is coupled to the control device, in order to control a rotational speed of the rotary magneto-resistive head. The control device can reduce the rotational speed of the rotary magneto-resistive head responsive to the read amplifier determining a presence of thermal noise in excess of a threshold, for example.
In a further representative embodiment according to the present invention, a force of contact between a cleaning roller and a rotary magneto-resistive head can be controlled by monitoring a current drawn by a drive motor turning a drum onto which one or more rotary magneto-resistive heads are mounted for the purpose of sensing an overload condition. If such a condition is sensed, a contact force of the cleaning roller against the rotary magneto-resistive head can be reduced by a control mechanism. In some specific embodiments, the ambient temperature and or the ambient humidity are accounted for when determining whether an overload condition exists in the drive motor.
In a yet further representative embodiment according to the present invention, an apparatus can comprise a motor current detector that is electrically coupled to a drive motor providing rotational motion to the magneto-resistive head, as well as to the control device, in order to provide an indication of a load placed on the drive motor by the cleaning roller contacting at least the rotary magneto-resistive head. The control device positions the cleaning roller out of contact with the rotary magneto-resistive head responsive to an overload condition detected by comparing the indication of a load provided by the motor current detector with a stored threshold that provides an indication of a current load of the drive motor with the cleaning roller not in contact with the magneto-resistive head.
In a still further representative embodiment according to the present invention, a method for cleaning a rotary magneto-resistive head can comprise a variety of steps. A step of selecting a verify/read mode of operation for the rotary magneto-resistive head can be part of the method. Further, the method can include detecting an error rate in excess of a threshold. Steps of halting travel of a magnetic tape adjacent to the rotary magneto-resistive head and positioning a cleaning roller in contact with at least the rotary magneto-resistive head can also be part of the method. The method also includes positioning the cleaning roller out of contact with the rotary magneto-resistive head responsive to an occurrence of either determining a presence of thermal noise in excess of a threshold, or a determination that the error rate has fallen below the threshold. In specific embodiments, the method can also include reducing a rotational speed of the rotary magneto-resistive head responsive to a determination of a presence of thermal noise in excess of a threshold.
In a still yet further representative embodiment according to the present invention, the method can also include a step of storing a threshold indicating a current load of the drive motor with the cleaning roller not in contact with the at least the magneto-resistive head. A threshold can be determined based upon an indication of current load, for example. Some specific embodiments can base the threshold on an ambient temperature and/or an ambient humidity, as well. A step of detecting a load placed on a drive motor by the cleaning roller contacting at least the rotary magneto-resistive head by sensing a current consumed by the drive motor is also part of the method. Further, the method can include the steps of comparing the indication of a load provided by the motor current detector with the threshold current load stored previously to detect an overload condition and controlling a force of contact between the cleaning roller and the rotary magneto-resistive head to eliminate the overload condition. Alternatively, some embodiments can position the cleaning roller out of contact with the rotary magneto-resistive head responsive to any overload condition detected.
In a still further representative embodiment according to the present invention, an apparatus for cleaning a rotary magneto-resistive head is provided. The apparatus comprises a cleaning device for a rotary magneto-resistive head. The cleaning device comprises a cleaning roller, positioned to contact the rotary magneto-resistive head and a conductive element positioned to contact the cleaning roller when the cleaning roller is not in contact with the magneto-resistive head.
In a still yet further representative embodiment according to the present invention, an apparatus for cleaning a rotary magneto-resistive head is provided. The apparatus comprises a cleaning device for a rotary magneto-resistive head. The cleaning device comprises a cleaning roller, positioned to contact the rotary magneto-resistive head. The cleaning roller has a conductive element positioned to contact the cleaning roller and routed through a member supporting the cleaning roller to a carbon brush that makes contact with a conductive leaf spring contact, which is connected to ground.
Numerous benefits are achieved by way of the present invention over conventional techniques. The present invention can provide methods and apparatus for cleaning contaminant from rotary magneto-resistive heads while guarding against damage to the head from excess cleaning, and the like. Specific embodiments can sense drive motor loading in order to insure that excess contact pressure is not placed on the rotary magneto-resistive head.